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Crossover Pipe Instead of Equalizer?

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Harry_6
Harry_6 Member Posts: 141
in Strictly Steam
OK, here's the deal: I've been doing work on a single-pipe steam system in a couple-thousand square-foot 1911 house. Two 2" mains originate at the boiler, circle their halves of the perimeter, and rejoin in the middle of the footprint, where their combined 2" return goes back to the boiler as a "dry" return. There is no vent or indication that there was one. All the piping looks original, but here's the thing: There is a 1" crossover line located over the boiler, connecting the beginning of one of the steam mains with the return main. I'm convinced it's original, since it uses cast fittings and a right and left hand threaded coupling. The current boiler is about ten years old and is plumbed in incorrectly in almost every way. No equalizer, no Hartford loop, steam riser goes a couple feet horizontal before vertical, it's a mess. My question is, could the original boiler not have had an equalizer and this crossover been an original attempt at that? Otherwise, it's just a short-circuit between the beginning and end of the same pipe. Anybody seen anything like this? (Sorry, no pic at the moment)

PS - I'm planning on removing the crossover and connecting a main vent in its place on the return. In the summer the boiler is getting repiped properly.

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  • STEVEusaPA
    STEVEusaPA Member Posts: 6,506
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    Everyone here likes pictures, or drawings...
    steve
    1Matthias
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,524
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    @Harry , I have seen an old system like that before in a really old library. The one I worked on had air vents on the returns. Of course they couldn't vent as steam would go through the crossover pipe into the return and close the vents. So now you have a steam main with steam pushing from both directions and the air trapped in between has no ware to go except out the radiator vents.

    Once we fixed it they told us the system never heated so good.

    If I were you I would put vents on the dry returns and the two dry returns shouldn't be connected above the water line. Either drop that tee below the water line or run both returns back to the boiler separately and drop at the boiler.

    And get rid of the dammed bypass, it will work much better. I don't know what they were thinking on your job or mine.
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,526
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    The original construction of this house predates the Hartford Loop. I believe they were trying to pressurize the end of the steam main to keep the water from backing out of the old coal-fired boiler. If there were no main vents, any air in the main would have been trapped between the two sources of steam. Condensate from the radiators can drain through the trapped air. Main vents would have screwed that up.

    None of this would have been ideal, however, and this is why the Hoffman Differential Loop showed up.
    Retired and loving it.
    Paul S_3
  • AMservices
    AMservices Member Posts: 610
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    The main with the 1" cross over to the dry return, is that T coming off pointing straight down, off the side or up at a 45ﾟ angle?
    Is that Main pitched away from the boiler or pitching back towards it?
    If the T is pointing down and the main is pitched towards the boiler ( Even for a couple of feet), it could be a drip.
  • jumper
    jumper Member Posts: 2,248
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    Is it plausible that the short circuit enables the return to do extra duty as an "auxiliary" supply main? I don't think so but...
  • jumper
    jumper Member Posts: 2,248
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    Another crazy idea. Since there are no main vents sending fresh steam through the return will push air in return up to radiator vents?
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,526
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    I think it's just an equalizer. They were making this up as they went along in those days.
    Retired and loving it.
  • Harry_6
    Harry_6 Member Posts: 141
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    Thanks everyone. An equalizer was my suspicion as well. It couldn't have been a drip, since it didn't come out the bottom of the pipe. I have also seen a number of these combined dry returns, and would have done it differently if it was mine to engineer, namely - as was suggested - separate them above the water line and vent them individually, since otherwise, if the loops are of different length, whichever steam gets to the vent first wins, and the air trapped in the other has to go out the radiator vents.

    Regardless, it's history now, replaced by a capped line on the supply side and a big 'ol air vent on the combined return. Works much better now.

    Also, FYI, in this house I had to reroute a steam line that passed through a wood timber beam (being removed)
    to accommodate a new steel beam. I did the textbook trick of over and under, and all's right with the world.

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